1. Field of the Invention
The invention relates to a polyamide blend molding compound with a polyamide blend content and at least one impact-resistant component according to the preamble of the independent claims 1 and 2. Such molding compounds are suitable, among other things, for the production of lines in industrial and automotive applications, preferably for vacuum lines and especially preferably for brake booster lines.
2. Discussion of Background Information
Plastic tubes made of polyamide are known and are used in many ways in vehicle construction for brake, hydraulic, fuel, cooling and pneumatic lines for example (cf. DIN 73378: “Polyamide tubing for motor vehicles”). Polyamide blend molding compounds with a polyamide blend content and an impact-resistant component are known from the patent application EP 1 942 296 A1 with respect to the production of hydraulic lines, especially clutch lines.
Plastic tubes or lines used in vehicle construction must meet a large number of requirements. In the case of a brake booster line, its function can be described as follows:
A brake booster is used on the brake of a vehicle to reduce the actuating force necessary for reaching a desired braking effect. This is especially necessary when disk brakes are used, because the actuation of the disk brakes of a car with the pedal pressure alone would require too much effort. In the case of vacuum brake boosters which are mostly installed in passenger cars and light commercial vehicles, the auxiliary force is generated by means of a pressure difference (atmospheric pressure to negative pressure). In the case of medium to heavy commercial vehicles (usually from 7.49 t) such as trucks for example the braking force is generated by means of compressed air, i.e. by means of a pneumatic power brake system. The operating pressure in this case is approx. 8 bar. In addition to this pneumatic brake booster, there are also hydraulic and electric ones.
Motor vehicles with classic gasoline engines require the use of a throttle under partial load in order to produce a combustible fuel/air mixture. A negative pressure is produced behind the throttle in the intake cycle (intake manifold) as a side effect. The brake pedal pressure is amplified in pneumatic brake boosters with the help of the intake vacuum or a vacuum pump. In the case of current gasoline engines with direct gasoline injection such as in the case of the VW TSI, a separate suction pump or vacuum pump is required due to the system-induced omission of the throttle, as is also the case in diesel engines (which principally also do not have a throttle). A non-return valve is installed in the connecting line between the brake booster and the vacuum source which is used for maintaining the vacuum under full load and engine at standstill. This vacuum represents a pressure gradient in relation to the outside air which can be utilized in the brake booster for increasing the braking force.
The vacuum or negative pressure is usually brought by means of tubing from the vacuum generator to the brakes or brake booster (BB). In order to ensure that it offers perfect functioning under all possible weather and temperature conditions, the following requirements, among other things, must be fulfilled by the brake booster line:
1) Material requirements on flexible lines “TL 52655”, brake booster lines (VOLKSWAGEN AG): Normal temperature range (continuous temperature TD≦120° C.); high temperature range (continuous temperature TD≦160° C.), sufficient strength up to at least +150° C. (over +160° C. in the short run). On the other hand, brake booster lines must also work securely even at temperatures of −40° C. It is also demanded that such brake booster lines are resistant against ozone and survive repeated change in climate without crack formation (with up to 20-60 cycles).
2) Worldwide Engineering Standards for Low Pressure Pipe Assembly for Brake Boosters “GMW 14640” (GENERAL MOTORS): Type A normal temperature range −40° C. to +110° C. (peak temperature up to +120° C.); type B high temperature range −40° C. to +140° C. (peak temperature up to +150° C.). This applies to line diameters 9±0.15×1.5±0.1 mm; 12±0.15×1.5±0.1 mm; 12.5±0.15×1.5±0.1 mm.
3) Delivery specs for tubes made of polyamide (PA) for the low-pressure range “DBL 6270”: (MERCEDES-BENZ): The pipes are subjected to heat ageing over 1000 hours at storage temperatures of up to +150° C. and then tested for impact resistance according to ISO 179 at 23° C. and −40° C. In the new state of the tubes, the impact resistance test occurs at 23° C., −40° C. and −50° C. The burst pressure test is performed according to DIN 53 758. Marking according to DIN 73 378 and FMVSS106/74 occurs for brake booster lines. DIN 74 324-1 and DIN 74 324-2 apply additionally to pneumatic brake systems. The product specification A116 000 66 99 and the norm FMVSS 106 apply additionally to tubes as vacuum lines for the operation of brake boosters (with the exception of Uni-mog).
The documents EP 1 329 481 A2 and DE 103 33 005 A1 are also known from the state of the art. Both deal with lines for vehicle construction, machine and apparatus construction, and medical engineering. In particular, these documents deal with the production of vacuum lines for brake boosters, ventilation lines, pressure hoses, pneumatic lines, control lines, coolant lines, fuel lines, vent lines, lines for windscreen washer systems, lines for hydraulic clutch systems, power steering lines, air-conditioning lines, cable or lead sheathings, or with injection-molded parts of an oil filter or fuel filter. EP 1 329 481 A2 discloses a molding compound which contains 99.9 to 95% by weight of a polyether amide on the basis of a linear aliphatic diamine with 6 to 12 C atoms, a linear aliphatic or aromatic dicarboxylic acid with 6 to 12 C atoms, and a polyetherdiamine with at least 3 C atoms per ether oxygen and primary amino groups at the ends of the chains. This molding compound is complemented at 100% by weight by 0.1 to 5% by weight of a co-polymer made of different chemical components.
DE 103 33 005 A1 discloses a molding compound which contains 97 to 80% by weight of a polyether amide on the basis of a linear aliphatic diamine with 6 to 14 C atoms, a linear aliphatic or aromatic dicarboxylic acid with 6 to 14 C atoms, and a polyetherdiamine with at least 3 C atoms per ether oxygen and primary amino groups at the ends of the chains. This molding compound is complemented at 100% by weight by 3 to 20% by weight of a caoutchouc containing functional grnups.
The product VESTAMID® EX9350 block is further known from the state of the art (VESTAMID® is a registered trademark of EVONIK DEGUSSA GmbH). It concerns a heatproof and weatherproof impact-modified polyamide 612 elastomer for extrusion processing during the production of tubing for example such as those for brake booster lines.
Blends of aromatic/aliphatic polyamides with different compositions are known from M. Xanthos et al. 1996 “Impact Modification of Aromatic/Aliphatic Polyamide Blends: Effects of Composition and Processing Conditions” (Journal of Applied Polymer Science, Vol. 62: 1167-1177). A polyamide blend molding compound is disclosed, having a polyamide content and at least one impact-resistant component, with said polyamide blend molding compound having the following composition:                32% by weight of an amorphous polyamide (PA 6I/6T) with an average of 7 C atoms per monomeric unit;        48% by weight of a polyamide (Nylon 6) on the basis of lactam and/or amino-carboxylic acid and with an average of 6 C atoms per monomeric unit, and        20% by weight of an ethylene/propylene elastomer (EPX) functionalized with maleic anhydride.        
Document U.S. Pat. No. 5,928,738 discloses a polyamide blend molding compound with a polyamide blend content and at least one impact-resistant component, with the polyamide blend molding compound comprising the following components:                30% by weight of a polyamide 6/12 (Grilon CF62) with an average of 9 C atoms per monomeric unit;        10% by weight of an amorphous polyamide 6I/6T;        50% by weight of a polyamide 6 on the basis of lactam and/or amino-carboxylic acid and with an average of 6 C atoms per monomeric unit, and        10% by weight of ethylene/methacrylic acid elastomer.        
Document U.S. Pat. No. 6,416,832 discloses a polyamide blend molding compound with a polyamide blend content and at least one impact-resistant component, with the polyamide blend molding compound comprising the following components:                20% by weight of a polyamide 6/12/MXD6 with an average of 8 C atoms per monomeric unit;        10% by weight of an amorphous polyamide;        50% by weight of a polyamide 6 on the basis of lactam and/or amino-carboxylic acid and with an average of 6 C atoms per monomeric unit, and        20% by weight of elastomers on the basis of polyethylene (AAE and PE).        
Document US 2005/0009976 A1 discloses a polyamide blend molding compound with a polyamide blend content and at least one impact-resistant component, with the polyamide blend molding compound comprising the following components:                45% by weight of a polyamide MXD6 with an average of 7 C atoms per monomeric unit;        25% by weight of an amorphous polyamide, and        30% by weight of a polyamide (PA6-NC2) on the basis of lactam and/or amino-carboxylic acid and with an average of 6 C atoms per monomeric unit.        
Document US 2007/0089798 A1 discloses a polyamide blend molding compound with a polyamide blend content and at least one impact-resistant component, with the polyamide blend molding compound comprising the following components:                50% by weight of a polyamide poly-meta-xylylene adipamide (MXD6) with an average of 7 C atoms per monomeric unit; and        50% by weight of a denatured polyamide 6 with an average of 6 C atoms per monomeric unit with a modulus of elasticity of 830 MPa.        
Document US 2004/0259996 A1 discloses the production of a polyamide blend molding compound with a polyamide content and at least one impact-resistant component, with the polyamide blend molding compound comprising polyamides and polyesteramides, nano-scale and fibrous fillers and impact-resistance modifiers. Ethylene propylene rubbers (EPM) and ethylene propylene diene rubbers (EPDM) are disclosed as impact-resistance modifiers.
Document JP 2001-329165 A discloses a reinforced polyamide composition with excellent flowability during injection molding with short cycle time. The reinforced polyamide composition leads to strong hot-glued or solvent-welded products and comprises 96 to 99% by weight of a crystalline polyamide, 0.1 to 4% by weight of a partially amorphous co-polyamide with at least two aromatic monomer components, and 5 to 200 parts by weight of an inorganic filler per 100 parts by weight of a polyamide resin.
Document EP 1 942 296 A1 discloses a molding compound on the basis of polyamide which is based on a mixture of the following components:                45 to 97% by weight of a polyamide 610 with an average of 8 C atoms per monomeric unit;        0 to 30% by weight of an amorphous and/or microcrystalline polyamide and/or co-polyamide;        2 to 20% by weight of an impact-resistant component in the form of a co-polymer on the basis of ethylene and/or propylene, and        1 to 10% by weight of additives.        